Generally speaking, an analog multiplexer comprises several channels respectively connecting several inputs to one output.
Each channel generally comprises a controllable CMOS circuit.
When the multiplexer is powered, one of the channels is selected for transmitting the signal present at the corresponding input to the output.
When the multiplexer is in the “cold spare” mode, it is not powered and it is capable of replacing another multiplexer to which it is connected in the case where this other multiplexer is defective.
However, in “cold spare” mode, the multiplexer must not interfere with the operation of the other multiplexer, notably in terms of current consumption.